View transmission system



VIEW TRANSMISSION SYSTEM OriginalFiled Feb. 28, 1931 Oct. 15,1940.

LNMWN. R W T2.- o# n M o m W5. .m `l||||n m c T .wml A Wm, 6m. /m m hm,\ l n .nl m .a a a o a a E W mi a d o @N N244/ a a a a m 0 a a a a mm f a mm1 ,a ,D w .i 9% I +H1 W u, ,qu D a .0 0| 0 im... .s M n :0| a 0. a a \\WUO\Q-\` am a f a p a M a a a E N o a W f6, a MWQA ,Patented Oct-.'15, 1940 A 4 .,UNIT PerEfNiaTf s VIEWTRANSMISSION/SYST'EM g u Randall C. Ballard, Audubon, N. J.; assignor to Westinghousel 'Electric &'Manufacturing1Com-` f Y l r pany, vEast'litt's'burghy .Pa;,.a'- corporation of Pennsylvania l i f i f '.Continuation ofiap'llilication S 4riall\'Io'.`i519,\0`62`, v

' Fcbruary'28,'1931. This .applicationDe'c'ember` y v323,19?, Serial N0.181,359`7 L. f' i. i., V g solaires., (amen-L27) 1 t 1 lhisinvention'relates to'ftclevision "andfac- 'to modulate.: @carrieryvavefin any wellknown simile-transmitting systemszandlit bears particu- `lmarmer f-for-feitherradio utransmissionto distant :lan r'elati'onslslipto systems especially adapted for "TBC'eVClS #01 tIflIiSHiSS-OH4 l,LKISIPO OVCT- metallic l :the: transriflissi/oniy andxreproduction, at a, distance, conductors,A These-details `are Ynot vdisclosed spef5 vG flrlovirxgpictures orath'e like.` g 1- cically as they do not comprise parts ofzthisjm y t Thisiapplioationis a' continuation of myfappliinvention.- This'portionof the system therefore, l :cation.Seriallblo-tlgl iled-Febifuary 28, 1931. `is merely1il5lustratedirl-the, formof a' rectangle 'fzThe primary object ofxthis inventionis to'fpr'o- -flabeled.rIfransmitterinserted.in the circuit; this deimpxoyedr'scauning.andreproducing-means "allpaaftusonsttung the*transmittingportion 10l -10".nisystemsioitheltype referred to above. fv Y of thesystem.L` f. ,Y l ,l .y lAnother fobjectioffthis invention isA to .provide HOneofvthe .outputterminals fvtheltransmit- :means :for-obtaining 'iaithful rvand vundis,torte'd reting apparatus is connectedto: a; distantly, located lfprddctioifmf movfrigipictures. J j receiver by :meansof l,a conductor Il) ,arid 13h@ 15 'Anothero-bjectrof:this invention is'vt'o provide `other terminalot'tlie.transmitter vis 'grounded. 15 meanswlierebyaccurate'synchronization maybe When -the transmission...iSbY letmmagnetc' fmaintaimed;Y t radiatiomthemetallic conductor isreplacedby j'Anogtheriob/iect 4oftthis-:invention is to provide anal-117911324. "Thedistantlyloatd rece/WH. might .z :scanmrxgcmeansxat:the receiving end of a `fac preferably comprise atplurality"ofhigli-frequency Zojfsme-tljansyltingisystem utilizing saw-tooth -amplifying stages; afderr'iodulator andjanl'audio- 20 iWave-formsl inzconnection lwith yelectromagne'tic frequely; amp'lfelf the vIJQ'JlT tlinSm'SSOniS dei'l'ectors for cathode rays. A accomplished through y*the modulation of acarrier 'AddPOYl'glOlQjeotSlofjtbis invention will'befdis- Wave.` i ,Y ,aclosedanncthefollowing"description-taken in Acon- A receiving.- galpalatu's Of-this type.llllfl'bifesv Y. 123 isiwithdrawn byaa take-up reel"5. t 41:rains'l-ucenceoflthe rtransnitted film;` may be v i Neither the driving mechanism employed in Y employed( 'Ihelamplitudegof tthe output must be -fjfth-froperatioriof fthe'fmm mechanism nor the i, sufiientto control the magnitudes of an electron ousual-.appalrltus.-Which'f'is rnormally employed in stream inacathode raytube: ISand; consequent- 'lfguidn'gtiie lr'n fb'erfore'lthe source of lightl .isf'disv .l-y, the..bri11iancy ivo'ffthe fluorescence, Where the 35 J3150Sidllilllucli,fvasfany of theconventional'type cathode'streamthrein strikesta screen y2| at the auatusriviaybe femploye'dfor this purpose. Vend of the tube. l "i f ThelightfromIaxedsourcelis relected'upon I The cathode raytubeis'preferably'of the type l nthe'vlm'frogiifanoscillatory mirror 9 vthat is so havingfavhelfmopc..Cathode.23.3 Control-element :U40Jarl'c'ai'i`gedsajsto V'periodically cause thereflected 25, .and anode 21, an` inductance 29 pro'ducing-a'n 40 'ggraygto 'passt'from side'ftoilsideof nthe film.' Any electromagnetic liield. for deflecting` the electron suitable means may bey provided fori'produ'oing Stream trarl'SlXl1Y`l1- a direction indicated by -z this.' oscillatory conditior1, such means being the arrowsffl, vand anotherl 'similar'inducta'nce .Y 'broadly indicated' `by-f` an inductor lil :energized 331.*positioned, atfright'angles to-'the inductance '-45 f 45* fr'omai'sourcecialternating currentl. .Aphoto- 2rfor'deiieting' theelectronstream'transaxially elestripCelll or: other flight-sensitive `devicel I'E'is infra directiontat QQ" tofthatjproduced'byj the lat- ,d inmediatelybehindthe'film 3 to receive terf "The'contro lectrode' 25 ofth'e cathode ray .-ztk'xeelightj yvvlii-ohm,flotas-1'become'modulated by.: the tubeisconnected -to the cathode ,tlfereofv through Dgfdg-YQGQflshadrigffthe picture elements a source of bisif-ptnti'alvandl an i-nput'imv f ight passes-therethroughy,-As Athe film nedaricecomprising'-resistor3l!I of lapiivroximately 150,' v 1in-:a-fdoivirward;(direction, indicated by the 50,000 ohms; the 4output circuit ofthe receivery l arrowigtiieiraygof iight reflectedirom the, oscilla- 5being-ooupledto theircoritrolf'electrode y25 by a si?? minor-3;fllauponeahframeof the lm, l condensera'l''having avalue of*` approximately 1 vcleii g V`ar-substantially'sinusoidalpath racross fmfdffuzl .l Y. A y ve, `.the ictureaareallhe longitudinal distance-onthe f v,The:potential vgradientbetween Ethe control 55K filmbetvgen successive .reversesfof the path being :@e1ectrodef25 andf'the cathode 23, comprises two 1,2 ctioijrof. tliepeed of .travel of 4v.the lm'and -components, aawdirect-curientbiasing t potential crateoirvibration,oft tliari'riirror.t` v from the direct-current' source-35 `andan ,alterl Af: @Qllltpllt Q llllent fl tli hOO-oell l5, nati-rigy potential representative ofthe-r modula- 5 f -tenit hasb'een sufcientlyiampliiied is utilized vt'kiorinoi the incoming. signal.;V .Sincevjthelmagnitude of the electron stream between the cathode and the anode is a function of the potential between the control electrode and the cathode, and, since the fluorescence of the screen 2I at the end of the tube I 9 is a function of the magnitude of the electron stream or the cathode ray passing through the electrode 25, it Will be apparent that the brilliancy of the fluorescence will, at any instant, be proportional to the picture modulation. One terminal of the inductance 29, hereafter referred to as the deflecting coil, is grounded and the other terminal is connected by a conductor 39 to one of the terminals of the alternatingcurrent source I3 which causes the mirror 9 to oscillate. The other terminal of the alternatingcurrent sourceis connected, through ground, to the winding of the inductor II which is associated with the oscillatory mirror and which functions to cause the vibrational movement thereof.

The deilecting coil 29, connected in circuit with the mirror-actuating coilof the inductor II, produces thehorizontal component in the scanning operation which occurs at the receiving end of the system. yTo provide means for producing the verticalscanning component at the receiving end of systems of the type described for the transmission and reception of motion pictures, it has been customary, according to the prior art, to

.employ the .charge voltage across a condenser which was charged at a constant current rate through a device, such as a saturated tube having a tungsten filament. This charge voltage was `applied directly to electrostatic deflection plates built into the cathode ray tube structure, and the electron beam was thereby caused to shift in a vertical direction. A system of this type is described in United States Patent 1,786,812.

V electrostatic deflection produced distortion of the focus of the spot of'light striking the fluorescent screen.

It mustbe borne in mind that thecharacteristics of the vertical scanning are entirely different from those of the horizontal scanning. In the one, namely, the horizontal, the velocity of travel of the cathode ray is substantially uniform in-both directions and it is a comparatively easy problem to cause the ray to oscillate at a uniform velocity by applying a sinusoidal voltage to the deecting coil. When providing the vertical scanning component however, the ray is caused to sweep acrossthe screen at one velocity and return to its starting place at a much higher velocity.

This change in velocity in opposite directions has been accomplished, as described, by means of electrostatically charged plates but, insofar as applicant is aware, no other means has ever been suggested whereby the cathode ray could be made to sweep across the screen at different velocities and in opposite directions when electromagnetic defiecting means are employed which overcome to a large extent the disadvantages noted above in respect to the use of electrostatic plates for this purpose.

Accordingly, this invention comprises an improvement upon the scanning means of the prior art by providing electromagnetic means for producing the results obtained by the electrostatic means of the prior art, at the same time energizing the electromagnetic deflectors by voltages of substantially saw-tooth waveform in an eilicient manner, with the consequent result that the received pictures will more faithfully reproduce the details of the originals.

The synchronous operation of the electromagnetic means referred to is accomplished by a make-and-break device forming part also of the subject-matter of United States Patent 1,786,812 previously referred to.

As the lm travels from the storage reel I to the take-up reel 5, it causes the rotation of a toothed wheel 4I, the teeth of which engage a series of marginal perfcrations in the film. The toothed wheel is connected through a shaft to a disc 43 that is provided with a plurality of peripheral projections 45. The free end of a contact member 4'I, by reason of spring action is caused to ride upon the periphery of the disc 43 except at such times as the projections on the disc cause the contact member to be lifted from the periphery. The diameter of the disc and the number of projections thereon are so chosen that one of the projections 45 raises the movable contact member 4l to engage a contact member immediately above it at each instant during the travel of the nlm 3 that the scanning ray is about to leave the upper edge of one of the pictures of the lm.

In the operation of the system, the lm, in its travel between the storage and the take-up reels, is exposed to a beam of light from the oscillating mirror 9 which moves in a substantially sinus= oidal path across, the lm at a frequency corresponding to that of the alternating-current source. At the same time, since one terminal of the alternating-current source I3 is connected to ground through the actuating winding of 'the mirror, and the other terminal is connected to ground through the deflecting coil 29A nearest the anode of the cathode ray tube, the electron stream in the cathode ray tube will be caused to oscillate from side to side in the direction of the arrows 3 I, at the same frequency that the ray of light is being caused to traverse the moving nlm. One coordinate of the scanning operation at the receiving end is accordingly provided by reason of the fact that the same source of alternating current actuates both the mirror and the cathode-ray beam.

It is necessary, however, to provide, at the receiving end, the other coordinate of the scanning operation corresponding to the longitudinal 'motion ofthe film at the transmitting end. Heretofore, as stated above, this coordinate was provided by the gradual building up of a `charge upon a condenser connected across a pair of deflecting plates. The gradual building up of the charge caused the beam of electrons to sweep from one end of the screen to the other in the same time that it takes `one picture of the film to pass through the light beam reflecting upon it. During the interim between the pictures on theflm, it is necessary that the electron beam be brought back to its initialposition before thelight beam reflected from the mirror 9 begins v to scan the succeeding picture. In other words, this time element will be equivalent to the time Should `the electron; bea-m,=forany reason, be

'it takes l'for that portion lofffllnl'betweenfpictures to traverse or pass through'ftlielight "bearrr4 sloWed up-on'its return tof-it'sf-initial starting position,v i1; wi11-be apparent -tna'tuistomenL win yoccur'in `thereceived picture: Circum'stances of ,this-nature rare prone to# occur inf the systems of the 'prior' art 'employing electrostatic deflection plates fory producing the vertical scanning com- `p'onent at the receiving end?, -thiszfbeing lcaused by reason of theresidual-charges building-,Wupy on the vglass .Walls 'ofthe tube7 Accordinglygbyf ern-l lploying electromagneticv :means v*ini lieuy 2 thereof, this possible defect yis eliminated/.fl

The vertical vscanning *component is produced in accordance with this invention by a gradual building` up of the magneticeld, L'andtlfle return lated bythe movementcof'theimovingepicturelm Yf'irfrii'iiall fpostion is brought about'by -:.a `sud'denl *collapse-f off theaiield thus build-up. These I results'aregaccomplished netizingl coil,the :operation 'ftl'ie systernrgbeing controlled lbyffthe make-rand-:break devicelactirsaw-tooth .scanningpctentials cer'nprisesiarltrfans` 'y former 49, thefprimaryiwinding-of whichiisccon- 'f 3ovnetted Aacross the makeandibreakfidevicerin :series With a source of?.l directecurretpotential'l .Theisecondary of thertrans'former constitutesithe -inputl1 circuitry-to .a hotecathode grid-glow :tube :53 'havingla cathode ,55,2 grid 1.5.1.; and aan anode y15! therein 'Ihexcathode'iist designed` iorfalte'rnating l current operation'its energy beingfderivedirom the secondaryofa: transformer ,f6-,I coupled Ato V` some suitable and1convenient:alternating-current source; 'not shOWn'here.

The output fcircuit'fof the gnd-{gmwtubeflsa Y comprises a resistorlliB-.inv series'withajsource oi high, potential of 1 approximately .2000' volts; the

y' "resistor V63 :being connected to thepositve terminal fof said source,A the negativeterminal/of which is groundedn ini-series; Wit-l1' the .resistor v,and one terminal of the high rv'potenti-al.source 1 isal condenser 65'in'suchfpositionzas to'reeive 4f. so

av chargegiromf-the source -of ,'.potential through the resistor-63.` ,The lmidpoint; of;l 'the 'cathode of -the grid-glow tubevfis1`-groundeld for `stabilizing purposes. The 1 resistanc'eftSi-ini the platecircuit' of the tube `534 functions to limit'theharging current for-the condenser 65 to a ,very lowgvalue,

`-Which,for all practical purposes",.is constant for short periods vof time.` :The high-voltage .source potential may be the sameas thatrequirediorthe operation of `the fcathode-.ray:.tube',z so that-fno additional high-potential source: is rlrequired.- for the purpose.V Y .4 i

The condenser 65..isadaptedto' charge-,to a `voltageof approximately 100 :voltsat Whichtime the impulse on Athe grid; of theitubecausedrby a yshort circuiting of the primary .by means of thefmake-and-break device', ,will cause .the gridlthe. condenser.

glow tube to breakl down and .suddenlyidischarge At .this pointitgmay.testate again triatin order to obtaingdeectionfin the""manner`pre viously described, `that i s,;at 'a 'certain velocityVV invcreasing at a uniform rate iorj'the r'noyementr oi thev cathode `ray in onedirection and ata much ihig'her velocity in the reversadirection 'in .order 'to return the ray as yquickly` as pess'ible to its vrorig- ,inal starting point, the deflectingmeans, Whether electrostatic or electromagnetic, must operate under the inuenceof *an-"electric currentyvhich aunif'ormvrate of 'increase/at a givenf-velocity from zero f to a kcertain Jmagntude in tirneffand a rapidV Vfall at, amuch lhigher 'velo'citybackjtofl zero. 'It is highly 'desirable rthat they rate vof `'has a speciedwaveform, referredtozasfa'rsaw-. `toothwave- The latterfis characteriz'edbyliaving movement of the beambe'u'riiform'ingoneifdithe .picture will appearfto be unequally illuminati ed; The saW-tooth'fwavefor'ml Voltage :accomplish'esthis very Well1 by"its' uniform@ra-tefof in'- y crease in time, and the rapidreturn` ofthesoa'n- `ning line is effected bythe-'quick fall tor Zero value of the current. As mentioned before, the` resistanceY capacity rcombination F65`-and t3 in con-I vjunction With the mechanically triggered .g'ri'd glowr tube providingva `sudden discharge fpath, is vthe 'source' generating a-Voltage of .substantially saW-tooth Waveform. 'In order to apply the VVoltage so obtained jeciently tol the. deflecting i coil" 33, there is provided a coupling circuit' including a highimpe'dance coupling devicevinthe forni of a vacuumtube 61 of the'screenrgrid type. Theinput --and output circuits, of-this tube are so arrangedfby properly chosennconstantsof` the .impedance -1 elements that the effect ofithe aanV ` inductive reactancewof the-coil '33Will" not react f upon the voltagesource, or influencethe' linear 'characteristics of the output current. The electrodes of thetube 61 are-connected :in .theaconventiona'l manner, VVthe-filament 15 beingenergized "by av suitablefjsourcev of fheatingfcurrent which in this case may be the transformerl employed 'for the Vfilament ofi the ygrid-glow tube53.y Operating potential 'for'the remaining electrodes arefshown schematically being obtained'iromtaps on a Voltage divider 83, which isconnected; across a source of approximately 600 l'volts D.'V C.v Taking,

the potential of the cathode :llas-:a reference point, itis seen-'that the screen V'His-isatv alpo-H. -tential more positivefthe'platel being at .'.th'e` most positive v-potential. The. plate kcircuit 'in- Vcludes the load" resistance lllz'andfa-` couplingconjdenser/85 of relatively-large capacityivaluaithe purpose of which is to isolate the-direct fcu'rrent component from the deflecting r coil 33 `which is enectively connected in parall'elfwith'the load' resistancelli The' inputfcircuit includes the 4"grid "1I, the gridresistor18H-Which returnsto l'ajpoint more negativer'vvith respect to the cathode 15 on.

the voltage divider-83.v {Thezinput circuit'fof `the tube 61..isenergized by the saw-tooth voltage produced 'by the oscillator arrangement previouslly described. Due to the fact that the Ascreen.l

grid tube, the 4function of which here is intendedfi.60

vto be. only a transmission controllingjelement, will inherently amplify, the `full output oftlie iy saW-t'oo'thycltage source is not applied to the -grid f thereof, butonly a portion between the condensersv 6-9 and'13,Which are in series-parallel connection and act as a Voltage divider.g1

Theoperation of th l is llargely dueto itsj'plate fvo'lta'geeplate current tube intheimannerf stated v*characteristic which is substantially "flat .Within 'Wide limits 'and'vvthe judicious choice?oficircuitv constants, Wherebythe? retroaotion for .ther-inductive reactancey of the .deflecting coil 'isesubstantially eliminated. In vtl'letyfygeifof'tl-lbe :.utilized e the'pla'te current is substantially unaiected by plate'voltage variations, and? thisicharacteristi fl the tube plays a predominant, part imm-operation of the circuit which -is designed to favor such operation by Virtue of the relations existing between the circuit constants. When the half cycle of oscillation is suddenly terminated bythe short circuiting action of the neon tube, the

rplate current drops immediately to its initial any other source than the input voltage to the tube, the output current waveform will conform to the input voltage waveform.

' During the interval of time when the contact 41 is riding upon the periphery of the disc 43,

Ythe plate current of the screen-grid tube r6'! will gradually and uniformly build up. The magnetic field in the laminated core will start `from a maximum value in one direction, decrease gradually, and uniformly pass through zero value and increase in the same manner to a maximum in the opposite direction. The resistor 8'! across the condenser and coil is of such high value as not to delay the reversal of current or the reversal of the flux in the coil 33 during the periods when the reversals take place. These periods of reversal occur when contact is made at the make-and-break device producing a pulse which, due to the discharge of the condenser 65 in the plate circuit of the grid-glow tube 53 suddenly causes the grid of the tube 61 to go negative, and the current through the deflection coil quickly reverses and returns to a maximum in the opposite direction, thus bringing the cathode ray back to its initial starting point in position for the starting of the scanning operation, as applied to the succeeding picture.

The circuit described may be adapted for use with' the conventional disc-type television scanning. For the horizontal scanning, the same circuit may be used, but it will beadvisable to use fewer turns on the deecting coilsI and to em,- ploy a five-electrode tube of higher plate current for the amplifier.

Inl a practical embodiment utilizing a screengrid tube known as the type 224, the following values of circuit constants were found to give the best results in obtaining saw-tooth current in the scanning coil 33 which had an inductance of approximately 10 to 20 henries:

Resistor 86 2 megohms Resistor 81 50,000 ohms l Condenser 85 8 micro-farads The operating voltages for the tube 61 were adjusted for linear response and the following conditions were found to give best results, with a plate potential source of approximately 600 volts, grid bias voltage approximately 4 volts negative, screen grid voltage 100V voltspositive with respect to the cathode '11. g

The above values are given merely by way of example for a practical embodiment of the circuit and are not intended to limit the application thereof to circuit constants other than shown above as long as in the operation of the system a saw-,tooth current is maintained in the scanning coil 33.

By reason of the fact that electromagnetic scanning devices are employed energized by saw- VI have disclosed my invention in great detail, I

do not desire to be limited thereto except as is necessitated by the prior art and the appended claims. v

I claim as my invention:

1. In an apparatus for controlling the -movement of a beam of cathode rays projected upon a screen, electromagnetic means arranged in proximity of said beam for controlling the transaxial movement thereof, an oscillator producing a voltage of substantially' saw-tooth wavev form, a transmission circuit coupling said oscillator with said means including a vacuum tube having at` least an anode, a control grid and a screen grid, means for energizing said screen grid, said vacuum tube having a plate-voltage, plate-current characteristic which is substantially at over the normal operating range of the plate current, an input circuit for said tube including said control grid and said cathode, said input circuit being energized by said oscillator, anoutput circuit between said anode and said cathode, said output circuit including said electromagnetic means.

2. In an apparatus for controlling the movement of a' beam of cathode raysprojected upon a screen, electromagnetic means arranged in proximity of said beam for controlling the transaxial movement thereof, an oscillator producing a voltage of substantially saw-tooth wave form, a transmission circut 'coupling said oscillator with said means including a vacuum tube having at least an anode, a cathode, a control grid and a screen grid, means for energizing said screen grid, an input circuit for said tube including said control 'grid and said cathode, said'input circuit being energized by said oscillator, and an output circuit between said anode and said cathode, said output circuit comprising an impedence effectively in parallel with a capacitor and saidelectromagnetic means.

3. In an apparatus for controlling the movement of a beam of cathode rays projected upon a screen, electromagnetic means arranged in proximity of said beam for controlling the transaxial movement thereof, an oscillator producing a voltage of substantially saw-tooth wave form, a transmission circuit coupling said oscillator Ywith said means including a vacuum tube having at least an anode,l a cathode, a control grid and a screen grid, means for energizing said screen grid, an inputl circuit for said tube including said control grid and said cathode, said input circuit being energized by said oscillator, and an output circuit between said anode and said cathode,v said output circuit comprising an-impedance eifectively in parallel with a capacitor and said electro-magnetic means, said impedance being of such magnitude and the operating characteristics of said tube so chosen as to produce a current in said output circuit which gradually and uniformly Vbuilds up to a maximum and then to quickly re- Verse.

Y RANDALL C.`BALLARD. 

